Mercury switch



Jan. 10, 1939. c, GEHRAND ET AL 2,143,002

MERCURY SWITCH Filed May 27, 1935 Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE MEnconY SWITCH "Application May 27, 1935, Serial No. 23,555

6 Claims. (Cl. 200 -112) This invention relates to mercury switches of the type disclosed in Larson Patent No. 1,967,247, in which the circuit throughthe switch is opened and closed by magnetically controlling the'posi tion (and hence the mercury displacement) of an iron armature in its relation to the mercury fill.-

It has been found in practice that the lower buffer spring on the armature or displacer will occasionally come loose and foul the switch; and it is the principal oblect of this invention to eliminate this possibility. This is accomplished by employing resilient means secured in some manner to a fixed part of the switch envelope, so

that not only is the switch made more certain of operation but also less power is required due to the elimination of the mercury friction that unavoidably results from carrying the lower buffer spring on the displacer.

Other and further objects will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig, 1 is a vertical cross-sectional view of a switch made in accordance with this invention;

Fig. 2 is a cross-sectional view taken on the line 22 of Fig, 1;

Figs. 3, 4 and 5 show other forms of the invention; and

Fig. 6 is a cross-sectional view of the form of the invention shown in Fig. 5, the section being taken on the line 6-8 of that figure.

It will be understood that the illustration and description of particular iormsof the invention 5 is for the purpose of disclosure only, and that the appended claims are not limited by the specific embodiments chosen unless required by the prior art.

Referring first to Fig. 1, the switch, generally 0 designated l0, comprises a glass envelope ii, through the base of which electrodes i2 and I3 are pinch sealed. The latter electrode is substantially centrally positioned within the en- .velope, and is surrounded by a glass sleeve ll to 45 a point slightly below the top of the electrode, leaving a bare end I! that is bent over below the top of the insulating sleeve for a purpose that is fully disclosed in Larson Patent No. 1,967,247. The envelope contains a mercury fill it, the

50 level of which is controlled by an armature or displacer, generally designated l1, consisting of an iron sleeve l8 surmounting a glass sleeve is, the latter having a slight bulge near its base that serves asthe seat for theiron sleeve II and permitsthe ironandglamsleeves Iland llto be held in flxedrelative position by a coil spring 2|, telescoped over the projecting end of the inher sleeve i9.

Movement of the displacer within the switch envelope is guided by washers 22, of hardened steel, the lower washer being positioned between the outer sleeve I8 and the bulge 20 of the inner sleeve I9, and the upper washer being clamped in place by the coil spring2i. The washers are provided with a plurality of lugs 23, that engage the walls of the envelope for maintaining the displacer in its proper axial position within the envelope.

The armature I7 is responsive to a coil 24, with which is associated an iron circuit 25, the latter being fully disclosed in'the Larson Patent No. 1,967,247, making it unnecessary to describe it in detail here.

Instead of employing a lower buffer spring, as shown in the Larson patentreferred. to above, it has been found desirable to provide a resilient seat for the displacer at the base of the switch envelope and to have the seat secured in some manner to a fixed part of the switch. This has the advantage that it removes the buffer spring from the displacer, and consequently reduces mercury friction with a resultant saving of power in operating the switch; and it also has the distinct advantage that it cannot possibly foul the switch such as a moving spring might possibly do.

In the form of the invention shown in Fig. 1, the resilient seat consists of a coil spring 26, preferably of tungsten or molybdenum wire, the spring being placed horizontally within the envelope and having its end turns engaging the envelope wall (Fig. 2) and intermediate turns engaging the central electrode i3. The material of which this spring is composed is sufficiently resilient to protect the base of the switch envelope from damage during shipping, or from overenergization of the relay, even though it is not positioned in the manner in which coil springs are ordinarily used.

In Fig. 3 a form of the invention is shown in which the resilient seat consists of resilient wire 21, preferably tungsten or molybdenum, spiraled about the central electrode i3, and having its two ends 28 projecting laterally for engaging the displacer.

It'is convenient to form-the resilient, seat on the central electrode prior to scaling the latter into the switch envelope, and this is done by forming spaced beads 29, 30, on the insulated electrode and then winding the wire 21 between is sealed into the envelope.

It is obvious that the wire 2'! may be wound on the sleeve M in a manner other than as shown in Fig. 3, for the laterally extending arms 28 atford suificient resiliency to protect the' base 01 the switch envelope.

In Fig. 4 the spring seat is a part of the electrode l2, the projecting end 3! being coiled about the central electrode and having its extreme end 32 frictionally engaging the latter electrode. Preferably the turn 33 of the coiled electrode rests on the floor of the envelope, so that stresses are not applied to the electrode 12, in a manner that may break the pinch seal. Obviously the electrode l2 may be used in a number of ways for protecting the base of the switch envelope from damage due to impact of the displacer.

In Fig. 5 a. special form of springseat is shown, which consists of a resilient clip 34, telescoped over the central electrode and having a substantially horizontal end portion 35, which forms the actual seat for the displacer. The clip 34' is also preferably of molybdenum or tungsten, these metals being sufiiciently resilient to accomplish the desired purpose and having no deleterious effect on the mercury because of electro-chemical reaction.

We claim as our inventionv 1. In a mercury switch of the class described, a switch envelope, a pair of spaced electrodes projecting into the envelope, a mercury fill, a magnetically responsive displacer for shifting the mercury level, one of said electrodes being .substantially centrally positioned within the switch envelope and havingan insulating sleeve surrounding it for a ortion of its length, and resilient means held in fixed position with respect to the switch envelope'by said central electrode for protecting the base of the switch envelope from damage due to impact of the displacer.

2. In a mercury switch of the class described,

a switch envelope, spaced electrodes projecting 'into the envelope, a. mercury fill, a magnetically responsive displacer forshifting the mercury level, and resilient means held in fixed position with respect to the switch envelope by one of the electrodes for cushioningdownward movement of the displacer as it approaches the base of the switch envelope, said displacer when in its upper position being spaced from the resilient means.

3. In a mercury switch, a vertical switch envelope, spaced electrodes in the envelope, a mercury fill, a magnetically responsive adapted to move in a vertical line within the envelope to displace more or less mercury depending on the direction of movement of the displacer, thereby to change the condition of the electrical circuit through the electrodes, a resilient element beneath the displacer for cushioning downward movement of the displacer. as it approaches the bottom of the switch envelope, said displacer when in its upper position being spaced from the resilient element, and means at the base of the envelope for anchoring the resilient element in fixed position at the lower end of the envelope whereby the resilient element as a whole is restrained from rising with the displacer when the latter is travelling upwardly with the envelope. V 4. Ina mercury switch, a vertical switch envelope, spaced electrodes in the envelope, a mercury fill, a magnetically responsive displacer adapted to move in a vertical line within the envelope to displace more or less mercury depending on the direction of movement of the displacer, thereby to' change the condition of the electrical circuit through the electrodes, aresilient element beneath the displacer ior cushioning downward movement of the displacer as it approaches the bottom of the switch envelope, said displacer when in its upper position being spaced from the resilient element, and means at the base of the envelope for anchoring the resilient element infixed position at the lower end of the envelope whereby the resilient element as a whole is restrained from rising with the displacer when the latter is travelling upwardly with the envelope,.said resilient element being formed as a part of one of said electrodes.

5. In a mercury switch of the class described, a switch envelope, spaced electrodesprojecting .into the envelope, a mercury fill, a magnetically responsive displacer for shifting the mercury level, and a coiled spring transversely telescoped over one of the electrodes and frictionally held thereby in fixed position with respect to the switch envelope for cushioning downward movement of the displacer as it approaches the base of the switch envelope, said displacer when in its upper position being spaced from the spring.

6. In a mercury switch, a vertical switch envelope, spaced electrodes in the envelope, a mercury fill, a magnetically? responsive displacen adapted to move in a vertical line within the envelope to displace more or lessmercu'ry depending on the direction of movement of the displacer, thereby to change the condition of the electrical circuit through the electrodes, a resilient element beneath the displacer for cushioning downward-movement of the displacer as it approaches the bottom of the switch envelope, said displacer when in its upper position being spaced from the resilient element, and means at the base of the envelope for anchoring the resilient element in fixed position at the lower end of the envelope whereby the resilient element as awhole' is restrained from rising .with the dis- .placer when the latter is travelling upwardly with the envelope, said resilient element being frictionallytelescoped over one of the electrodes and having a laterally extending bu'fier arm adjacent to its top. w I

CLARENCE E. GEHRAND. CARI. H. LARSON. 

